The present invention relates to industrial air preheaters, and more particularly, to apparatus and method for detecting and suppressing so-called "hot spots" in regenerative, rotary heat exchangers.
U.S. Pat. No. 4,383,572, issued on May 17, 1983 to K. Bellows for a Fire Detection Cleaning Arrangement, describes an infrared sensing array for the rotor of a rotary regenerative heat exchanger adapted to view the infrared ray emission from the rotor at a plurality of radially distinct zones. In the system disclosed in the '572 patent, and other systems using a variety of analogous detection techniques, the entire area of the rotor can be monitored. Conventionally, when a hot spot is sensed within the rotor, an alarm is energized requiring operator intervention in various forms. Depending on the circumstances, this can involve energizing deluge or suppression systems, opening access doors and utilizing fire hoses, or similar corrective action. Thus, conventionally, responding to the hot spot detection system alarm of the prior art, requires manual operations and can consume valuable or even critical time. It is well known in this field that hot spots can, if not cooled quickly enough, lead to combustion of trapped deposits in the matrix of the rotor. These can rapidly escalate to temperatures high enough that the metal rotor bursts into flame, potentially causing extensive damage not only to the heat exchanger, but to other equipment and components in the plant.